Elevators usually have a drive machine which drives the elevator car under control of an elevator control system. The drive machine typically comprises a motor and a rotatable drive member, such as a drive wheel, engaging an elevator roping which is connected to the car. Thus, the driving force is transmitted from the motor to the car via the drive member and the roping. Conventionally, elevators have a counterweight suspended by a rope section that is on one side of the rotatable drive member and the car by the rope section that is on the other side of the rotatable drive member. The counterweight provides tension for the rope section which does not suspend the car. There are also elevators which do not have a counterweight. These counterweightless elevators have the car suspended by the rope section that is on one side of the rotatable drive member, whereas on the opposite side the elevator comprises some sort of tightening arrangement for tightening the rope section on that side of the rotatable drive member. In these tightening arrangements, formation of loose rope in large scale is typically eliminated by connecting the rope on both sides of the rotatable drive member to the car with same ratio. Thereby, during upwards directed movement of the car also the rope section not suspending the car travels along with the car thereby not piling up anywhere in the hoistway. Furthermore, the tightness may be further increased with a tightening device. This may be needed for one or several of the following reasons. Firstly, by increasing the rope tension of the rope section not suspending the car it is possible to ensure that the rope rests against the rotatable drive member firmly for the whole length of contact between these components, in particular so that a normal force adequate for providing firm engagement between these components is provided. Secondly, in this way the rope tension of the rope section not suspending the car can be increased so as to ensure that the ropes do not jump away from their guide pulleys positioned along the route of the ropes. Furthermore, the rope length in many elevator arrangements changes slightly as a function of car position. The problems caused by this phenomenon can be eliminated by tightening the rope section not suspending the car. There are numerous different existing counterweightless elevators, for example elevators as disclosed in WO2004041699A1.
With existing counterweightless elevators, there have been difficulties to make the system such that the layout of the rope arrangement as well as the overall structure of the tightening arrangement are simple and compact. A drawback has been that the roping has needed a great number of ropes arranged in a complex layout. Also, in existing solutions, it has been difficult to design and dimension the tightening arrangement in a compact fashion yet such that it enables an adequate capacity of tightening. In particular, the range of movement of the movable tightening members has been designed and dimensioned long. A drawback has been that the space consumption of the tightening arrangement as well as the roping has made their space-efficient positioning difficult.